Electrical apparatus



J 1964 R. N. YECKLEY ETAL 3,113,956

ELECTRICAL APPARATUS Filed Nov. 21, 1960 2 Sheets-Sheet l INVENTORS Russell N. Yeckley 8 Rober? G. Colcloser BY W F-M ATTORNEY Jan. 21, 1964 YECKLEY ETAL 3,118,966

ELECTRICAL APPARATUS 2 Sheets-Sheet 2 Filed Nov. 21, 1960 United States Patent 3,118,966 ELECTRKCAL APPARATUS Russell N. Yeekiey and Robert G. Colclaser, in, Monroeville, Pa, assignors to W estinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Filed Nov. 21, 1960, Ser. No. 70,576 5 laims. (Cl. 17418) The present invention relates to electrical apparatus in general and, more particularly, to electrical apparatus of the type having a terminal-bushing structure which extends into a tank containing electrical apparatus and having a dielectric gas therein.

A general object of the present invention is to provide improved electrical apparatus having a liquid-type terminal-bushing structure associated therewith, in which differential pressure across the one or more seals of the terminal-bushing structure is eliminated, to prevent entrance of the dielectric gas disposed within the tank structure from entering interiorly within the body of the terminalbushing structure.

A more specific object of the present invention is an improved terminal-bushing structure having gas passage means associated therewith to transmit gas from the body of a tank, with which the terminal-bushing structure is associated, up through the terminal-bushing to the upper surface of the liquid level within the terminal-bushing to thereby equalize the pressures imposed upon the terminalbuslr'ng seals.

A more specific object of the present invention is to provide an improved oil-filled terminal-bushing structure having a tubular terminal stud extending axially therealong for the transmission of pressure into a gas space disposed at the external end of the terminal-bushing for subjecting the liquid within the terminal-bushing to the same pressure as is present within a gas-fi1led tank structure, with which the terminal-bushing structure is associated. Preferably, a flexible diaphragm, composed of a suitable material, such as neoprene, is employed to prevent direct contact of the transmitted gas with the oil within the terminal-bushing.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 is an end elevational view of a circuitinterrupter tank structure embodying the improved terminal-bushing structure of the present invention; and,

FIGS. 2A and 2B collectively show an enlarged sectional view taken along the terminal-bushing illustrating the improved terminal-bushing structure of the present invention.

In United States patent application filed January 23, 1959, Serial No. 788,668, now United States Patent 3,057,- 983, issued October 9, 1962 to Benjamin P. Baker, Russell N. Yeckley and Joseph Sucha, and assigned to the assignee of the instant application, there is disclosed and claimed a novel gaseous-type circuit-interrupting structure utilizing a dual-pressure, closed-cycle system, in which it is desired to utilize a highly effective interrupting gas at high pressure. Preferably this gas, following interruption, is exhausted into a low-pressure system, and a compressor is provided which functions to recompress the relatively low-pressure gas and force it under high pressure, back into the high-pressure system. The circuit interrupter of the foregoing patent application is of the sulfur-hexafluoride (SP gas-type,and the highly eifective interrupting performance of this gas renders the circuit-interrupting structure suitable for very high-power application.

In the sulfur-hexalluoride (SF gas-type circuit interrupter, such as described in the aforesaid patent application, sulfur-hexa'tluoride gas-filled terminal-bushings, such as set forth in United States patent application filed iliifiiib Patented Jan. 21, 1964 "ice December 2, 1959, Serial No. 856,775, now United States Patent 3,059,044, issued October 16, 1962 to Robert E. Friedrich and James H. Frakes may be employed. In such an eventuality, the sulfurhexafiuoride gas from the tank structure may be permitted to seep through a hollow terminal stud associated with the terminal-bushing and permitted to pass between the insulating shells and the terminal stud of the terminal-bushing, thereby serving as a dielectric gas for the terminal-bushing.

However, such gas-filled bushings, although having a major advantage by providing a substantial reduction in height obtained, have a somewhat disadvantage by supplying a potential tap, which requires a transistorized amplifier, such as set forth in United States Patent 2,924,726, issued February 9, 1960 to John F. Reuther, and assigned to the assignee of the instant application. For simplicity, and also to meet some customer demands, a liquid-filled, such as an oil-filled, bushing could be used. A strong factor in favor of the use of such a liquid-filled bushing is its long history of trouble-free performance. Possible moisture problems may also be eliminated by the use of such a liquid-filled terminal-bushing. Because of its unique use in a gas-filled breaker, a shortened oil-filled bushing could be used with a conventional potential tap.

An objectional factor, however, is the possibility of the sulfur-hexafiuoride (SP gas leaking through the interior bushing seals, causing voids in the oil, and possibly increasing the pressure inside of the porcelain shells associated with the terminal-bushing. The arced SP gas would also have a deleterious elfect upon the paper condenser employed in such a liquid-filled terminal bushing.

It is an object of the present invention to provide a solution to the problem of eliminating the pressure diiferential upon the terminal-bushing seals and thus removing the possibility of the sulfurhexafluoride gas leaking into the bushing. As a result, the quality of the seals at the lower interior end of the terminal bushing would not have to be perfact since the pressure differential is eliminated.

With reference to FIG. 1 of the drawings, it will be noted that a circuit-interrupting apparatus 1 is shown including a tank structure 2, having end caps 3, 4, out of which an interrupting assemblage 9 may be laterally removed. Associated with the upper portion of the tank structure 2 are a pair of cylindrical mounting supports 5, 6, which support a pair of terminal structures '7, 8 fixedly in position. A mechanism housing 11 is disposed adjacent one end of the three-pole circuit interrupting structure 1, as shown. Disposed within the mechanism housing 11 is suitable operating mechanism and compressor equipment, not shown, which functions to maintain the proper high pressure within a high-pressure tank, at high potential, associated with each of the interrupting struc/ tures 9 disposed within the several tank structures 2.

As shown, there is a single tank structure 2 and a pair of terminal-bushings '7, 8 for each pole-unit of the interrupter 1. For controlling a three-phase transmission line, preferably three such tank structures 2 are disposed in alignment and an operating rod 12 extends lengthwise of the three tank structures 2 and interconnects movement of the operating mechanism within housing 11 with the movable contact structure in each of the three pole-units.

Reference may be had to the aforesaid Patent 3,057,983 of Baker, Yeckley and Sucha for a detailed description of the arc-extinguishing assemblage 9 disposed in each of the three tank structures 2. For the purpose of understanding the present invention, however, it is only necessary to know that gas under pressure is provided in each of the three tank structures 2, and that terminal-bushings 7, 3 are provided to conduct current into and out of the tank structure 2 for controlling the associated transmission line.

FIGS. 2A and 2B collectively show more clearly the internal construction of each of the terminal-bushings 7, 8. It will be noted that a weather-proof shell 13 is provided externally of the tank structure 2, and a dielectric body, such as a condenser body 14, surrounds a tubular terminal stud 15 for withstanding the high voltage existing between the terminal stud 15 and the grounded mounting flange 16 of the terminal-bushing 7. Preferably, mounting bolts 17 are employed to fixedly secure the terminalbushing 7 in a proper position with reference to the mounting cylinders 5, 6.

Disposed adjacent the interior end of the terminalbushing 7 is an interiorly disposed casing 21 composed of a suitable material, such as porcelain, which serves to prevent mixing of the sulfur-hexafluoride gas within the region 22, interiorly of the tank structure 2, and the region 23, within the terminal-bushing 7 about the condenser body 14. within which a suitable liquid such as oil, is disposed to prevent air voids being present. The liquid, such as oil 24, completely fills the space between the interiorly disposed condenser body 14 and the two weatherproof shells 13, 21 and passes longitudinally through a ground sleeve 25.

A potential tap structure 26 is provided, which is normally grounded, but may, at times, be empioyed to measure the voltage present on the terminal stud 15.

With reference to the lower end of the terminal-bushing 7, it will be noted that a gas-tight seal 27 is provided between the lower end surface 28 of the porcelain casing 21 and a lower plate support 31, which is threadedly secured at 32 to the lower threaded end 33 of the holiow terminal stud l5.

Suitable springs 34 provided within a cap structure 35 provide pressure exerted upon the casings 13, 21., to maintain pressure upon the seals 27, 3d, 37 and an additional seal 38 at the upper end of the terminal-bushing 7.

It will be noted that the gas pressure within the region 22 may be of the order of 60 psi. Normally, the gas pressure of the nitrogen gas, which is usually above the liquid level of an oil-filled bushing, of conventional type, is only 8 or 9 pounds. With such a conventional oil-filled terminal-bushing, there would be a differential pressure associated with the seals 27, 3:: which might tend to cause the entrance of the sulfur-hexafluoride gas into the space 23 within the terminal-bushing 7.

To avoid the entrance of sulfur-hexafluoride gas, due to such a differential pressure, past the seals 27, 36 and into the region 23, to contaminate the oil, the tubular terminal stud 15 is provided, which transmits the gas pressure from within the tank structure 2 up into a gas space 41 upon the upper surface of the liquid level through vent openings 19. Additional openings 26 in a flange portion 35a of the cap structure 35 assist in such communication of gas pressure. To prevent direct contact between the sulfur-hexafluoride gas within the gas space 41 and the upper surface of the liquid 24, preferably a pressure-transmitting partition means such as a flexible diaphragm i2 is provided so that the gas pressure may be imposed upon the liquid, but yet no direct contact therebetween is afforded.

The outer end of the tubular terminal stud 15 is threaded, as at 15a, to threadedly secure into place a supporting end portion 29. The end portion 29, as shown, has radially outwardly extending arms 29a serving as upper seats for the compression springs 34. Additionally, the supporting end portion has a shoulder 2% provided thereon which abuts the inner periphery of the flexible diaphragm 42 in sealing relation. A ring-shaped backup plate is disposed on the other side of the inner periphery of the flexible diaphragm 42, and a clamping nut 39 is threaded onto a threaded portion 290 of the end portion 29.

A cap wall portion 35a has a shoulder 35b formed thereon to sealingly engage the outer periphery of the races flexible diaphragm 42. A sealing ring 4% has a plurality of circumferentially-spaced apertures as provided therein to accommodate a plurality of sealing bolts 39 which are threaded into tapped holes 35c of the cap structure 35. The result is a gas and oil seal provided by the flexible diaphragm 42 between the supporting end portion 29 and the portion 35a of the cap structure 35, with the diaphragm on, or close to, the liquid surface.

To prevent excessive deflection of the diaphragm, which may be made of neoprene, a perforated backup plate 43 is provided. As a result of this construction, there is imposed upon the liquid .24 the same pressure as exists within the tank structure 2. Consequently, there is no differential pressure existing upon the seals 27, 36 within the interior of the tank structure 2 and the seals consequently do not have to be of unique construction since no differential pressure exists thereacross.

Another advantage of the construction is that the use of the diaphragm 42 permits ease of handling the bushing during manufacturing or assembly, since the bushing may be positioned horizontally during handling.

From the foregoing, it will be apparent that we have provided a novel terminal-bushing structure of the liquid type which may be associated with electrical apparatus, such as circuit-interrupting apparatus disposed within a tank structure filled with a dielectric gas. Although a circuit interrupting apparatus has been illustrated as a possible embodiment of the invention, it will be obvious to those skilled in the art that the present invention may be applied to transformer apparatus, in which a tank structure is provided filled with a dielectric gas, and terminalb-ushings are employed to bring current into and out of such tank structure. Merely for purposes of illustration has the present invention been shown in connection with circuit-interrupting apparatus. In addition, although sulfur-hexafluoride gas has been illustrated as the gas employed within the tank structure 2, it will be obvious to those skilled in the art that other gases may be employed, and that the present invention is applicable wherever it is desired to prevent differential pressure upon the seals associated with a terminal-bushing structure.

Although there has been shown and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim as our invention:

1. Electrical apparatus including a tank filled with an insulating gas, a liquid-filled terminal bushing extending within said gas-filled tank for the purpose of carrying current thereinto, terminal-stud means extending axially through the terminal bushing and having an end supporting portion, cap means defining a gas space within the terminal bushing adjacent the external end thereof above the liquid level, means providing a gas passage longitudinally through the terminal bushing from the interior end thereof to said gas space at the exterior end thereof above the liquid level within the terminal bushing, pressure-transmitting partition means including a flexible gasimpervious diaphragm, supporting means for supporting said flexible diaphragm substantially on the liquid surface between the liquid level and said gas space, said supporting means including said end supporting portion and a cap wall portion of said cap means, whereby the liquid Within the terminal bushing is subjected to the same pressure as the gas within the tank to eliminate differential pressure on the one or more seals disposed at the interior end of the terminal bushing.

- 2. Electrical apparatus including a tank filled with an insulating gas under pressure, a liquid-filled terminal bushing extending within said gasafilled tank for the purpose of carrying current thereinto and having a seal at the interior end thereof, terminal stud means extending axially through the terminal bushing and having an end supporting portion, cap means defining a gas space within the terminal bushing adjacent the external end thereof above the liquid level, means providing a gas passage longitudinally through the terminal bushing from the interior end thereof to said gas space at the exterior end thereof above the liquid level Within the terminal bushing, pressure-transmitting partition means including a flexible gas-impervious diaphragm, supporting means for supporting said flexible diaphragm substantially on the liquid surface between the liquid level and said gas space, said supporting means including said end supporting portion and a cap wall portion of said cap means, whereby the liquid within the terminal bushing is subjected to the same pressure as the gas within the tank to eliminate differential pressure on said seal disposed at the interior end of the terminal bushing.

3. Electrical apparatus including a tank filled with an insulating gas, a liquid-filled terminal bushing extending within said gas-filled tank for the purpose of carrying current thereinto, terminal stud means including a tubular terminal stud extending axially through the terminal bushing and having an end supporting portion, cap means defining a gas space within the terminal bushing adjacent the external end thereof above the liquid level, means including said tubular terminal stud providing a gas passage longitudinally through the terminal bushing firom the interior end thereof to said gas space at the exterior end thereof above the liquid level within the terminal bushing, pressure-transmitting partition means including a flexible gas-impervious diaphragm, supporting means for supporting said flexible diaphragm substantially on the liquid surface between the liquid level and said gas space, said supporting means including said end supporting portion and a cap wall portion of said cap means, whereby the liquid within the terminal bushing is subjected to the same pressure as the gas within the tank to eliminate differential pressure on the one or more seals disposed at the interior end of the terminal bushing.

4. Electrical apparatus including a tank filled with an insulating gas under pressure, a liquid-filled terminal bushing extending within said gas-filled tank for the purpose of carrying current thereinto and having a seal at the interior end thereof, terminal stud means including a tubular terminal stud extending axially through the terminal bushing and having an end supporting portion, cap means defining a gas space within the terminal bushing adjacent the external end thereof above the liquid level, means including said tubular terminal stud providing a gas passage longitudinally through the terminal bushing from the interior end thereof to said gas space at the exterior end thereof above the liquid level within the terminal bushing, pressure transmitting partition means including a flexible gas-impervious diaphragm, supporting means for supporting said flexible diaphragm substantially on the liquid surface between the liquid level and said gas space, said supporting means including said end supporting portion and a cap wall portion of said cap means, whereby the liquid within the terminal bushing is subjected to the same pressure as the pressurized gas within the tank to eliminate differential pressure on said seal disposed at the interior end of the terminal bushing.

5. A liquid-filled terminal bushing having a tubular terminal stud, said tubular terminal stud having an end supporting portion, a solid dielectric body disposed about the tubular terminal stud extending lengthwise along the terminal bushing, at least one weather-proof insulating shell, a dielectric liquid disposed between the inner wall of the weather-proof shell and said solid dielectric body, cap means defining a gas space at one end of the bushing above the liquid level, pressure-transmitting partition means including a flexible gas-impervious diaphragm, supporting means for supporting said flexible diaphragm substantially on the liquid surface between the liquid level and said gas space, said supporting means including said end supporting portion and a cap wall portion of said cap means, passage means interconnecting the space within the tubular conductor stud with said gas space, whereby the liquid within the terminal bushing is subjected to the same pressure as the gas within the tank to which the terminal bushing is applied to eliminate differential pressure on the one or more seals disposed at the other end of the terminal bushing.

References Cited in the file of this patent UNITED STATES PATENTS 2,223,409 Skvortzofi Jan. 14, 1941 2,315,666 Skvortzoif Apr. 6, 1943 2,981,815 Leeds et a1. Apr. 25, 19 1 

1. ELECTRICAL APPARATUS INCLUDING A TANK FILLED WITH AN INSULATING GAS, A LIQUID-FILLED TERMINAL BUSHING EXTENDING WITHIN SAID GAS-FILLED TANK FOR THE PURPOSE OF CARRYING CURRENT THEREINTO, TERMINAL-STUD MEANS EXTENDING AXIALLY THROUGH THE TERMINAL BUSHING AND HAVING AN END SUPPORTING PORTION, CAP MEANS DEFINING A GAS SPACE WITHIN THE TERMINAL BUSHING ADJACENT THE EXTERNAL END THEREOF ABOVE THE LIQUID LEVEL, MEANS PROVIDING A GAS PASSAGE LONGITUDINALLY THROUGH THE TERMINAL BUSHING FROM THE INTERIOR END THEREOF TO SAID GAS SPACE AT THE EXTERIOR END THEREOF ABOVE THE LIQUID LEVEL WITHIN THE TERMINAL BUSHING, PRESSURE-TRANSMITTING PARTITION MEANS INCLUDING A FLEXIBLE GASIMPERVIOUS DIAPHRAGM, SUPPORTING MEANS FOR SUPPORTING SAID FLEXIBLE DIAPHRAGM SUBSTANTIALLY ON THE LIQUID SURFACE BETWEEN THE LIQUID LEVEL AND SAID GAS SPACE, SAID SUPPORTING MEANS INCLUDING SAID END SUPPORTING PORTION AND A CAP WALL PORTION OF SAID CAP MEANS, WHEREBY THE LIQUID WITHIN THE TERMINAL BUSHING IS SUBJECTED TO THE SAME PRESSURE AS THE GAS WITHIN THE TANK TO ELIMINATE DIFFERENTIAL PRESSURE ON THE ONE OR MORE SEALS DISPOSED AT THE INTERIOR END OF THE TERMINAL BUSHING. 